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AMERICAN MINK (NEOVISON VISON) CONTROL IN PROTECTED AREAS IN POLAND -MONITORING OF THE ERADICATION EFFECTIVENESS
A. Niemczynowicz1, M.Brzezinski2, A. Zalewski1
^Mammal Research Institute, Polish Academy of Sciences, Bialowieza, Poland aniemczynowicz@ibs.bialowieza.pl
department of Ecology, University of Warsaw, Warsaw, Poland
Biological invasion is a major threat to biodiversity and ecosystem function as the negative impacts of invasive on native species can be devastating. Reducing the density of invasive species is an important goal in protected areas. Understanding the mechanisms that underlie compensatory responses in populations of invasive species has the potential to enhance the effectiveness of control programmes.
American mink (Neovison vison) is a semi-aquatic species, endemic to North America, which was introduced in the wild in Europe in the 1930s. In many introduced areas, the American mink has an excessive predation impact on waterfowl and riparian mammals, leading to a marked decrease in their density. The aim of this study is to analyse colonization rate of mink after eradication in the 3 National Parks of Poland: Drawa National Park (DNP) situated in western Poland, Biebrza National Park (BNP) and Narew National Park (NNP), situated in eastern Poland (Fig. 1).
The American mink eradication programme was conducted at two areas in each of the National Park: eradication area [EA] (where mink were removed) and control area [CA] (where mink were marked and released). At both areas, live box, wire-mesh traps were deployed on the banks of rivers 500 m apart. Trapping sessions were 5 days long and traps were visited once per day. Mink trapping was conducted in five trapping sessions (March-April 2009, Novem-ber-December 2009, March-April 2010, November-December 2010 and March-April 2011). In 2009-2011, during the spring and summer, 20 rafts were deployed in each national park on the river where mink were trapped (10 at the eradication area and 10 at the control area) to monitor the population of mink and determine the effectiveness of mink eradication program. Rafts are floating platforms with a footprint-recording plates made of moist clay and sand that are placed under wooden tunnel on the platform base (Fig. 2).
Figure 1. Location of the three National Parks in Poland
Rafts were placed at 1-km intervals and were checked every two weeks for the presence/absence of mink tracks. The percentage of rafts with mink tracks was calculated for the whole study period. The percentage of rafts visited by mink at control area and eradication area in consecutive years was positively correlated with the number of mink trapped in spring (r=0.71, n=9, p=0.033 and r=0.85, n=8, p=0.007, respectively). At eradication area, the percentage of rafts visited was 10% lower than at control area, and this was associated with lower mink densities during spring-summer (Fig.3).
Figure 2. Mink raft
Even though long-term effects of mink removal were not evident, our results suggests that on a local scale, eradication of mink undertaken in late autumn and early spring decreased mink density during the breeding season, which overlaps with the breeding season of birds (April-June). Therefore, we may expect that mink pressure on native prey at eradication sites is temporary lower as compared to the areas where mink are not removed. The results of this study conducted in Polish national parks confirm that mink raft monitoring reliable assesses mink density and recolonisation rates. The local and shortterm reduction of invasive species numbers seems possible, however, recolonization removes the effect of eradication within few months.
% visited raft
N mink captured
Figure 3. Relationship between the number of mink captured at control area and at eradication area and percentage
of rafts with mink tracks
